Bypass regulator? Or orifice?

[Scotty_S-15]

I plan to use my return line to the tank. I'm tapping off the end of the fuel line/log at my Holley HP 750, and use a .026 orifice. Does this plan suck? Is .026 too small? Too big? Or should I spring for a new bypass regulator?

................ I've recently been having a problem with the the truck crapping out while driving on the street. Happened twice, both hot days, and it was a fuel issue. Suspect vapor lock and/or pump getting hot & tired. Nothing has changed on the truck, no previous problems in nearly 10 years of V8 use.

............ So I got a new Holley Gerotor 12-125 pump, and read some info from Holley: "....... potential vapor lock issues that may occur due to the sensitivity of new fuels! Aha. the new F'n fuels. The regulator I have is the one they recommend for this new pump. Or, they also recommend their bypass regulator if potential vapor lock problems exist. That's me. http://www.s10v8.com/images/smilies/icon_mad.gif

.............. But I'm thinking that it would be better for performance to use an orifice at the end of the fuel log, as opposed to the bypass regualator, because the fuel going to the secondaries would never get hot because of the return flow. Sure, a tiny bit does flow through the secondaries because of the idle circuit, but I don't guess that it's that much.

........... Obviously I don't want to be starving my secondary bowl. But that .026 orifice wouldn't do that. Or would it? http://www.s10v8.com/images/smilies/icon_confused.gif

[stroker1]

I see your point. If you are doing alot of street driving I guess your pump could run the risk of getting hot. Especially for the old pump. As for the orifice V/S the bypass regulator, isn't that really what a bypass regulator is anyway?? It has to have some type of orifice to only allow X amount of fuel to get past it.



I am wondering something! Do you regulate the flow going into the fuel log on you set-up? Or do you regulate the flow after the fuel log? If you put an orifice in the system, I think it would definately make a difference on pressure consistancy depending on if you had the orfice before or after the regulator.



Lots of Questions that I certainly don't know the answer to. But long story short you are trying to create a bypass regulator without buying a bypass regulator. So I think you should mimic the bypass regulator as closely as possible. They make them the way they do for a reason, I would guess. There are people who create their own bypass regulators. Maybe cruise the forums on Dragstuff.com and you might read something on there.



Or just spend some of that rusty old money and spring for a new bypass regulator. http://www.s10v8.com/images/smilies/icon_razz.gif



Stroker1

[Scotty_S-15]

Thanks for the thoughts Stroker.

* Yeah, I've always had a "thing" about getting rid of hot fuel. and I think what I've planned will work better than just a bypass regulator.

* Concerning the "fuel log", that was an inaccurate way to describe it. Here's a pic of what I did last night. My Holley has the option to feed the fuel bowls from either side, hence a "plug" opposite the fuel inlet. Most Holleys have a boss, but it's not machined out. So really the fuel is being bled off near the secondary needle and seat.

* My fuel pressure gauge and FP sending unit is between the primary and secondary fuel inlets, so I'm thinking that if there is a problem, the gauges should show it.

* And concerning the .026" orifice, I simply looked at my # drill bits, and picked one, eeny, meeney, miney, moe. http://www.s10v8.com/images/smilies/icon_razz.gif Oh yeah, the orifice is in the flare fitting adapter. I filled the pipe thread end with solder and drilled it.

* My regulator is mounted on the front of driver's side cyl. head, isolated from metal, just above (past) my fuel filter. Then about 16" of steel line to the std. chrome Holley Wye (log).





Holley blank fuel inlet, drilled & tapped for 1/8" pipe. (http://i154.photobucket.com/albums/s267/Scotty_S-15/DSCN1294a.jpg)



* And oh yeah, regarding how the bypass regulator works: I dunno. But I just assumed that it had an orifice, BUT, through the valving, the orifice would be closed when regulator was in max flow mode. Again, just an assumption.

[rayL]

for what its worth scotty alot of nitrous guys use a .020 "bleed" on there fuel side of the nitrous to keep the pressure constant. It works there so i dont see why it wouldnt for you. what would be cool is to maybe get a jet holder and tap it into your fuel log and keep upping the jets till you get your pressure right and just do away with the regulator all together. heh..might work.

[Scotty_S-15]

Ray: That's why I love this site. Guys like you have all the great ideas! I had some .025 air bleeds, (my smallest) and a 10-32 tap, #21 drill bit. So now I've got a .025 orifice that I can easily change!

.......... And thanks for giving me some comfort and confidence, knowing that the nitrous guys do this too.



Flare adapter drilled for 10-32 (http://i154.photobucket.com/albums/s267/Scotty_S-15/DSCN1300a.jpg)

[stroker1]

Hey Scotty, how did it work out?? Did the fuel flow through the other side of the fuel bowl?? Kinda seems like the needle valve would be getting a work out like this!! I can say that it's given me an idea for more constant fuel pressure though. But just not bleeding the bowls off like you did.



So what happened?? Stroker1 http://www.s10v8.com/images/smilies/icon_confused.gif

[Scotty_S-15]

Results inconclusive at this point. http://www.s10v8.com/images/smilies/icon_confused.gif I only drove it a few times after installation, and the weather wasn't terribly hot. I'm thinking that maybe I'll need to open up that orifice a little, to get additional flow back to the tank. I say that 'cause I broke the line and started it up, and just a slight dribble was coming out. I guess .025 ain't much at 6 psi.

............. And as we speak, the truck is all apart, changing heads & cam. I'm headed out to 'er right now to prep the block head surface & chase the head bolt holes, then I'll degree the old cam to know where I was at, then whip in the new cam, and degree it. By then, it ought to be about midnight. http://www.s10v8.com/images/smilies/icon_razz.gif Seriously, I doubt if I'll get that far today, 'cause I'll be needing to chase the lawnmower around the yard later. http://www.s10v8.com/images/smilies/icon_wink.gif

[mzoomora]

I plumbed my return with a valve on it, it was an inline compression fitting valve, kinda similar to what you would use on a refrigerator. It worked great and never ran the truck out of fuel. It was run off of the second port of my fuel regulator. You could also run one of those holley fuel logs that have an in and an out, run it wide open into the fuel log and then plumb a regulator on the back side. That is similar to the way many fuel injected vehicles come from the factory, like TBI's, the regulator is after the fuel is delivered.



So it would go pump - carb - return with regulator. The regulator would bleed of excess pressure after it is used.



http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2D220101&N=70 0+4294924496+4294821621+4294865540+115&autoview=sk u

[stroker1]

On 2007-08-11 17:16, mzoomora wrote:

I plumbed my return with a valve on it, it was an inline compression fitting valve, kinda similar to what you would use on a refrigerator. It worked great and never ran the truck out of fuel. It was run off of the second port of my fuel regulator. You could also run one of those holley fuel logs that have an in and an out, run it wide open into the fuel log and then plumb a regulator on the back side. That is similar to the way many fuel injected vehicles come from the factory, like TBI's, the regulator is after the fuel is delivered.



So it would go pump - carb - return with regulator. The regulator would bleed of excess pressure after it is used.



http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2D220101&N=70 0+4294924496+4294821621+4294865540+115&autoview=sk u

Funny you brought that up. I just logged on to do the very same. I saw this a few days ago with a local guy with a prostreet s10. I was gonna think about it a little before I posted, so last nights post I just left it out. The guy is pumping into one end of the fuel log. Then comes out in 2 different places and goes to each bowl. Then another 1/8th NPT fitting with a guage. At the far end of the fuel log is a diaphram regulator with each outlet plugged. Then the return port is a #6 pushlock hose going back to the fuel cell. The gage reads the same when the engine is switched off and the pump running as it does at WOT. And idle is also the same. The only difference is the amount of fuel returned to the fuel cell, so he says.



Hey I saw the gage readings and they where very still. Just barely a wiggle in the needle. That sure beats the hell out of running a holley blue dead headed against a regulator and into the carb. We all know how the pressure creeps up on them.



Stroker1